1. Field of the Invention
This invention relates to the long term stabilization of an enzyme contained in detergent compositions using proteins containing quaternary nitrogen substituents.
2. Prior Art
The desirability of using enzymes in cleaning compositions is well known. Lipase enzymes, for example, are useful for their ability to reduce macromolecules such as fats into smaller glycerol and fatty acid components which can be readily washed away by detergents and/or water. Detergent compositions containing these enzymes are capable of removing fatty stains. Protease enzymes, for example, are useful for their ability to reduce proteinaceous stain which can then also be readily washed away.
The stability of enzymes, e.g., lipases and proteases, in current liquid detergent compositions, however, is generally poor due to various reasons. First, the surfactant found in such detergent compositions induces denaturation of the enzyme. Second, when a protease is present in the composition, the protease will cause proteolytic digestion of the other enzyme, if it is not a protease, or of itself in a process called autolysis.
Proteins, such as those taught in U.S. Pat. No. 4,842,758 to Crutzen (Colgate-Palmolive) and U.S. Pat. No. 4,842,767 to Warschewski et al (Colgate-Palmolive), are known to improve enzyme stability in heavy duty liquids (HDLs). There is no teaching in these patents, however, of the use of proteins containing quaternary nitrogen substituents for enzyme stabilization.
Other approaches used for stabilization of enzymes in HDLs include the use of aminated polysaccharides such as taught in U.S. Pat. No. 4,011,169; the use of calcium and carboxylic acids (preferably formate) such as disclosed in U.S. Pat. Nos. 4,305,837, 4,490,285 and 4,537,707; the use of calcium with alkyl diacids (succinic, adipic) such as disclosed in U.S. Pat. No. 4,529,525; and the use of aliphatic glycols with and without boron containing compounds such as taught in U.S. Pat. Nos. 3,819,528, 4,462,922, 4,404,115 and 4,652,394.
West German published patent application No. P 29 37 012.5 (Henkel) teaches agents for stabilizing enzymes which are the protein reaction products of (1) ammonia or primary or secondary amines containing up to 20 carbon atoms and/or (2) aliphatic epoxides containing 2 to 18 carbon atoms to protein substrates. Proteins used as substrates for addition of these groups include gelatin, collagen, zein, casein, soy protein and other plant proteins as well as so-called single-cell proteins. Gelatin, collagen or casein are said to be preferred.
The Henkel application teaches only the use of primary or secondary amines compared to the tertiary or quaternary amines used in the invention.